Various machines or power drive mechanisms require the use of a clutch between a drive member and a driven member to establish selective engagement therebetween when power or torque is applied to the drive member. In such applications, it is highly desirable that the clutch be automatically and instantaneously responsive to the application of power to the drive member to effect engagement with the driven member and to maintain such engagement until the power is removed, at which time the clutch will automatically disengage the members. This is prevalent in engaging and disengaging drive axles of vehicles, for instance. Often there may be locking means which may be automatically or manually disengaged to immobilize the clutch.
Similar types of clutches may be used in aircraft applications where a turbine driven starter drives an engine through an overrunning clutch assembly. A gearbox conventionally is coupled between the starter and the engine. Ideally, hot gases power the turbine that turns the engine to be started. Once the engine speed exceeds self-sustaining speed, power to the starter is shut off and the overrunning clutch disconnects the engine from the turbine to prevent high speed backdriving. The overrunning clutch also is effective to allow the engine and gearbox to continue to operate should the starter turbine jam. Relatively large torque is required to drive the engine. However, problems would occur and not be compensated for should malfunctions occur in the starter itself, such as bearing and overrunning clutch failures or the like.
Accordingly, a need exists for a shaft decoupling mechanism that is effective at a small back torque to disconnect the starter from the engine.